The overhaul of the Chiefs’ defense has had its share of casualties, but Saturday’s roster cuts took another step toward reshaping the team.

Fourth-year safety Bernard Pollard and veteran linebacker Zach Thomas were the headliners of Saturday’s mandatory roster purge, as the Chiefs released 13 players and placed offensive lineman Colin Brown, a former Missouri player, on injured reserve.

The Chiefs also waived wide receiver Ashley Lelie, who was signed during training camp and was considered a potential speed threat for an offense that was stagnant through four preseason games, all losses.

The moves came a day after the Chiefs purged their corps of offensive linemen, letting go of veteran tackles Damion McIntosh and Herb Taylor. They released two other linemen Friday and another, guard Darryl Harris, on Saturday. With Brown’s move to injured reserve, one of the team’s weakest position groups is now down to eight players — the expected starters plus three reserves.

Coach Todd Haley has said the Chiefs would scour the waiver wire throughout the preseason, hoping to add talented players to a roster that became noticeably devoid of them. The offense scored two touchdowns in four games, and the quarterbacks frequently had to scramble to avoid constant pressure.

Haley wasn’t available to reporters Saturday.

The Chiefs kept their four quarterbacks, and they’ll move forward with plenty of passers but few reliable blockers to keep those quarterbacks healthy. Matt Cassel has a leg injury that kept him out of Thursday’s preseason finale at St. Louis, and the team hasn’t said whether he’ll be healthy in time for the regular-season opener next Sunday at Baltimore.

Health seemed to stand between Thomas, a seven-time Pro Bowl linebacker, and a 14th NFL season. He suffered an undisclosed injury early in training camp and missed all but five practice days. Thomas was expected to provide a veteran presence the team missed last year when it began a youth movement that has reshaped the roster but hasn’t led to many wins. During this year’s offseason practices, Thomas was seen as a mentor to young and veteran defenders, and linebacker Derrick Johnson said last month that Thomas’ leadership was valuable enough to warrant the veteran a roster spot, even if he couldn’t play.

“Everybody looks to Zach on everything,” Johnson said during training camp. “Zach is very much needed on this team.”

Age and health might have hurt Thomas’ chances, but those reasons didn’t apply to Pollard’s release. Pollard, a 24-year-old strong safety, was often the target of criticism for poor tackling and lackluster fundamentals, and the Chiefs signed veteran Mike Brown to push Pollard to improve on his weaknesses.

“Mike is a great player,” Pollard said after the Chiefs’ first preseason game. “Obviously, he’s played for nine years and been to the Pro Bowl. He’s a great guy and a great player.

“We’re going to compete against each other for the rest of the year. It’s not just going to be a one-time competition. We’re going to compete all the time and we’re going to try to bring the best out of each other.”

Pollard appeared to respond, spending almost all his time with the first-team defense during training camp and the preseason. Still, the Chiefs were reportedly trying this week to trade him.

Pollard’s release was an additional step by the Chiefs’ leadership to distance the team from the past. Pollard was a second-round pick in 2006, and he started 31 games in three seasons. With Pollard’s release, the Chiefs will begin the 2009 season with just 14 of the 26 draft picks taken during former coach Herm Edwards’ three years. Running back Kolby Smith, a fifth-round pick in 2007, was placed on injured reserve Friday.

If the released players clear waivers, they could be added to the Chiefs’ practice squad.